The present invention relates to the diagnostic imaging arts. It finds particular application in conjunction with SPECT nuclear imaging systems and will be described with particular reference thereto. It will be appreciated, however, that the present invention is useful in conjunction with other systems that utilize penetrating radiation, and is not limited to the aforementioned application.
Typically in nuclear imaging, a source of radioactivity is used to provide non-invasive diagnostic images. The source is typically injected into a patient, although external sources are also utilized. Radiation from the source traverses at least a portion of the patient and is detected by radiation detectors.
Typically, a nuclear camera has one, two, or three detector heads. Each head has a large scintillator sheet, such as doped sodium iodide, which converts incident radiation photons into scintillations, i.e. flashes of light. An array of photomultiplier tubes is disposed in back of the scintillator to monitor for light flashes. The output of the photomultiplier tubes and associated circuitry indicates the coordinates of each scintillation on the sodium iodide crystal and its energy. Unfortunately, there are numerous non-uniformities and inaccuracies when using a large scintillator crystal and an array of photomultiplier tubes.
The heads have collimators disposed between the crystal and the subject to limit the trajectory along which radiation can be received. Typically, the collimators are thick lead plates with an array of apertures or bores. Radiation traveling in a trajectory through one of the bores strikes the crystal; whereas radiation traveling in other trajectories hits the collimator and is absorbed. In this manner, each scintillation defines a ray, typically perpendicular to the face of the crystal although magnifying and minifying collimators are also known. The thicker the collimator, the more accurately the ray trajectory is defined, but more radiation is absorbed in the collimator without reaching the detector.
To improve the amount of radiation that reaches the detector, it has been proposed to use collimator sheets in a single direction across a row of detectors such that detected radiation defines a plane instead of a ray. The detectors are rotated to collect the planes at many angles. For three-dimensional images, the detector was positioned at a plurality of locations around the subject and the rotating data collection process repeated. The images from the rotating data collection technique had artifacts due to non-uniformities in the data sampling.
The present invention provides a new and improved method and apparatus that overcomes the above referenced problems and others.
In accordance with one aspect of the present invention, a method of diagnostic imaging is provided. A radioactive isotope is introduced into a subject. The isotope decays and radiation indicative of nuclear decay events is detected by a rotating solid state detector array to produce planar projections. The detector is moved around the subject, gathering a plurality of different views of the subject. The detected radiation emissions are reconstructed into an image reconstruction of the subject.
In accordance with another aspect of the present invention, a diagnostic imaging apparatus is provided. A means for transmitting radiation transmits radiation that is detected by a means for detecting after passing through a portion of a subject. A first rotating means rotates the detecting means about a longitudinal axis of the subject. A second rotating means rotates the detecting means about an axis perpendicular to the longitudinal axis while the detecting means detects radiation. A means for reconstructing reconstructs the detected radiation into an image representation of the subject.
In accordance with another aspect of the present invention, a diagnostic imaging apparatus is provided. A detector array detects xcex3-ray emissions that pass through a portion of a subject in an imaging region. A rotation drive rotates the detector array about an axis orthogonal to the detector array. The rotation drive is mounted to a gantry for rotation about an axis of the subject. A reconstruction processor reconstructs detected xcex3-rays into an image representation of the subject in the imaging region.
One advantage of the present invention is that it presents a small, relatively light nuclear detector array.
Another advantage is that it presents a solid state nuclear detector array.
Another advantage is that provides uniform sampling over an imaging volume.
Another advantage is that radial resolution is conserved.
Another advantage is that angular sampling rates are conserved.
Another advantage resides in uniformly distributed data points.
Still further benefits and advantages of the present invention will become apparent to those skilled in the art upon a reading and understanding of the preferred embodiments.